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The apparent detection of an exoplanet orbiting Fomalhaut was announced in 2008. However, subsequent observations of Fomalhaut b raised questions about its status: Unlike other exoplanets, it is bright in the optical and nondetected in the infrared, and its orbit appears to cross the debris ring around the star without the expected gravitational perturbations. We revisit previously published data and analyze additional Hubble Space Telescope (HST) data, finding that the source is likely on a radial trajectory and has faded and become extended. Dynamical and collisional modeling of a recently produced dust cloud yields results consistent with the observations. Fomalhaut b appears to be a directly imaged catastrophic collision between two large planetesimals in an extrasolar planetary system. Similar events should be very rare in quiescent planetary systems of the age of Fomalhaut, suggesting that we are possibly witnessing the effects of gravitational stirring due to the orbital evolution of hypothetical planet(s) around the star.

In this paper, I re-examine the question of a possible explanation of the anomalous advance of Mercury’s perihelion by the existence of the hypothetical planet Vulcan proposed by Le Verrier, whose orbit would be located inside the orbit of Mercury. My calculations are focused on the optimization of the orbital parameters of Vulcan in order to explain precisely the anomalous advance of Mercury’s perihelion. To reach this goal, I have used recent experimental results concerning intra-mercurial zone observations to constrain the range of orbital elements for Vulcan. My calculations establish the direct relation of the anomalous advance of Mercury’s perihelion with the mass of Vulcan and its distance to Mercury, which confirms the failure of the Vulcan hypothesis since to explain the anomalous advance of Mercury’s perihelion one obtains an unrealistically large mass for Vulcan, even larger than that of Mercury.

This article presents the results of an analysis of Tisserand’s constant for 1389 long-period comets in relation to a hypothetical planet. A mechanism is proposed to apply Tisserand’s criterion for a relatively trans-Neptunian planet with a notable inclination and orbit eccentricity. In particular, the algorithm considers the planet’s heliocentric distance in the era of a clearly-defined transformational change in the cometary orbit. Thus, we carried out the corresponding calculations by simulating the planet motion plane. This study allows a comparative analysis of Tisserand constant values for proposed hypothetical planet parameters. The most notable result is for a planet at a proposed distance of 340 AU.

As the scientific community's unofficial defender of reason against the onslaught of \"cosmophobia,\" planetary scientist David Morrison sees a long year or so ahead for him. The Internet is roiling with warnings of doom from the sky. Alien beings are rumored to be steering Comet Elenin our way to knock Earth off its axis. Worse still, other sites assure us, a rogue planet called Nibiru is barreling through space to trigger the end of the world on 21 December 2012. Elenin is real enough, scheduled to make a distant flyby of Earth in mid-October. Nibiru, astronomers say, exists only in the fears of credulous denizens of the Web. But one thing is certain: As the scientific community's unofficial defender of reason against the onslaught of such \"cosmophobia,\" planetary scientist David Morrison sees a long year or so ahead for him.

Ever since Pluto lost its status as one of the main planets of our solar system and was demoted to just another frozen denizen of the Kuiper belt, we have had to make do with eight, albeit in a pleasing symmetry, with four rocky ones this side of the asteroid belt and four giants on the far side. Now it looks like number nine is back on the slate: the existence of a large planet, about ten times as massive as Earth and hundreds of times more distant from the Sun than Earth itself, has been postulated to explain the curiously bunched-up orbits of several small celestial bodies, far beyond the orbit of Neptune. To date, we have only \"proof by simulation\" and we are yet to observe this massive planet in the backyard of our solar system by more direct means. However, powerful new telescopes should provide visual evidence within the next few decades.

A list of selected binary stars is presented that have been observed for several decades using a 26-inch refractor at the Pulkovo Observatory. These stars are at a distance from 3.5 to 25 pc from the Sun. They belong to spectral classes F, G, K, and M. Their masses range from 0.3 to 1.5 solar masses. We have analyzed them as possible parent stars for exoplanets taking into account the physical characteristics of these stars. In view of dynamic parameters and orbital elements that we have obtained by Pulkovo observations, ephemerides of positions for the coming years are calculated. The boundaries of the habitable zones around these stars are calculated. The astrometric signal that depends on the gravitational influence of hypothetical planets is estimated. Space telescopes for astrometric observations with microsecond accuracy can be used to detect Earth-like planets near the closest stars of this program. This paper presents an overview of astrometric programs of searches for exoplanets.

Although the architectures of compact multiple-planet systems are well-characterized, there has been little examination of their \"outer edges\", or the locations of their outermost planets. Here we present evidence that the observed high-multiplicity Kepler systems truncate at smaller orbital periods than can be explained by geometric and detection biases alone. To show this, we considered the existence of hypothetical planets orbiting beyond the observed transiting planets with properties dictated by the \"peas-in-a-pod\" patterns of intra-system radius and period ratio uniformity. We evaluated the detectability of these hypothetical planets using (1) a novel approach for estimating the mutual inclination dispersion of multi-transiting systems based on transit chord length ratios and (2) a model of transit probability and detection efficiency that accounts for the impacts of planet multiplicity on completeness. Under the assumption that the \"peas-in-a-pod\" patterns continue to larger orbital separations than observed, we find that \\(\\gtrsim35\\%\\) of Kepler compact multis should possess additional detected planets beyond the known planets, constituting a \\(\\sim7\\sigma\\) discrepancy with the lack of such detections. These results indicate that the outer (\\(\\sim100-300\\) days) regions of compact multis experience a truncation (i.e. an \"edge-of-the-multis\") or a significant breakdown of the \"peas-in-a-pod\" patterns, in the form of systematically smaller radii or larger period ratios. We outline future observations that can distinguish these possibilities, and we discuss implications for planet formation theories.

In this paper, I re-examine the question of a possible explanation of the anomalous advance of Mercury's perihelion by the existence of the hypothetical planet Vulcan proposed by Le Verrier, whose orbit would be located inside the orbit of Mercury. My calculations are focused on the optimization of the orbital parameters of Vulcan in order to explain precisely the anomalous advance of Mercury's perihelion. To reach this goal, I used recent experimental results concerning the observations of the intra-mercurian zone. My calculations establish the direct relation of the anomalous advance of Mercury's perihelion with the mass of Vulcan and its distance to Mercury.

The loneliness of hot Jupiters supports the high-eccentricity migration as a primary path leading to the formation of systems with those planets stripped of any close-in planetary companions. Here we present the null results of searches for low-mass planets close to hot Jupiters in 10 planetary systems: HAT-P-4, HAT-P-10, HAT-P-12, HAT-P-17, HAT-P-19, HAT-P-32, HAT-P-44, Qatar-6, TrES-4, and WASP-48. We employed multi-sector time-series photometry from the Transiting Exoplanet Survey Satellite enhanced with new ground-based transit light curves to determine the sizes of hypothetical planets that might still avoid being detected. We redetermined transit parameters for the known hot Jupiters using a homogenous approach. We refuted transit timing variations for HAT-P-12 b, claimed recently in the literature. The transit timing data permitted us to place tighter constraints on third bodies in HAT-P-19 and HAT-P-32 systems detected in Doppler measurements. We also study four multi-periodic pulsating variable stars in the field around HAT-P-17.

A long tradition of research initiated by Luria in the 1930s has established that unschooled adults perform poorly on reasoning tasks. Particularly when the premises are unfamiliar, they adopt an inappropriate empirical bias. However, recent findings show that young children with little or no schooling reason competently if prompted to think of the unfamiliar premises as pertaining to a distant planet. We tested two groups of adults: illiterate, unschooled adults and adults with limited schooling. Both groups received problems that included either a premise with unknown content or a premise contradicting their everyday experience. When given a minimal prompt, both groups manifested the customary empirical bias. By contrast, when explicitly prompted to think of the unfamiliar premises as pertaining to a distant planet, they reasoned accurately and appropriately justified their conclusions in terms of the supplied premises.